Week 7 Pharmacology


  • Eg Gentamicin
  • bacteriocidal
  • Used mainly against Gram negative enteric bacteria, sepsis, TB
  • Not effective against anaerobes cos needs O2 dependent transport into cytoplasm.
  • Water soluble, don’t go into CNS or eye
  • Partial diffusion, partly active transport into the cell–> bind to 30S ribosome–> intefere with initiation of complex peptide formation, misreading of mRNA, breakup of polysomes into monosomes.
  • Poorly orally absorbed so usually given IV, t1/2 – 2-3hrs
  • Renally cleared
  • Once daily dosing – more effective due to concentration dependent killing, significant postantibiotic effect(actio persists beyond time when measurable drug is present). Less time in the toxic levels. More convenient – better compliance, less nursing required, can be done as outpatient.
  • Narrow therapeutic index
  • SE – ototoxicity, nephrotoxicity(especially if Rx for more than 5d, elderly, renal imp, higher doses). Resp paralysis via NMJ blockade at very high doses – reversed with calcium gluconate.
  • Increases effect of neuromuscular blocking agents



  • Eg sulfamethoxazole
  • Structure is similar to PABA
  • Inteferes with folate production and therfore DNA synthesis (doesn’t affect mammal cells cos we get exogenous folate)
  • Bacteriostatic alone, bacteriocidal with trimethoprim.
  • Cover gram positive and negative, norcadia, chlamydia, and some protozoa.
  • Synergistic when used with trimethoprim cos that acts at the sequential step of folate synthesis.
  • SE -fever, rash, exfoliative dermatitis, photosensitivity, nausea, vomiting, diarrhoea, stevens johnson syndrome. Can crystalise in urine –> haematuria or obstruction. Haemolysis, granulocytopenia, thrombocytopenia.



  • Interferes with folate synthesis by inhibiting dihydrofolic acid reductase



  • Eg ciprofloxacin, moxifloxacin
  • Block bacterial DNA synthesis by inhibiting topoisomerase II(DNA gyrase) and IV.
  • Cover gram positive and negative, pseudomonas
  • Oral Bioavail – 80-95%, t1/2 – 3-10hrs, renally excreted
  • SE – nausea, vomiting, diarrhoea, QT prolongation. Not for use in under 18yo due to damage to growing cartilage.



  • Inhibits nucleic acid synthesis in anaerobes
  • Good for anaerobes and protozoa esp c diff
  • “nitromidazole”
  • SE – nausea, diarrhoea, abdo pain, metalic taste, hypersensitivity, disulfram effect if taken with etOH.



  • TB treatment needs multiple drugs and good compliance for at least 6mo. Isoniazid, rifampin, pyrazinamide, ethambutol. (RIPE)



  • – amphotericin B – puts hole in lipid membranes of cells – toxic to humans in high levels.
  • Azoles – ketaconazole etc – inhibit fungal > human cytochrome P450 so less cell wall is made.
    Nystatin – like ampotericin – for local candida infections
  • (Same with antimalarials and antihelminthics)




Aciclovir (has been asked).

  • Acyclic guanosine dervative
  • HSV 1 and HSV 2 >>>>VZV, In genital herpes it shortens symptom duration by 2d and viral shedding by 7d
  • 3 step activation, the first step requires viral thymidine kinase – so specific–> third step product inhibits viral DNA polymerase –> inhibits viral DNA synthesis
  • Oral bioavail – 15-20%, T 1/2 – 2-3hrs, renally cleared.
  • Long term suppression of recurrent genital herpes, IV for herpes encephalitis.
  • Weak against cmv



  • Nucleoside reverse transcriptase inhibitor
  • Used in HIV/AIDS


Principles of HIV therapy

  • Start treatment if CD4 count <200 or viraemia high or opportunistic infection
  • Use Highly active antiretroviral therapy – multiple agents to avoid resistance.
  • Nucleotide reverse transcriptase inhibitor
    • Competitively inhibit HIV 1 reverse transcriptase
    • Eg lamivudine – cytosine analog when incorporated it results in premature termination of DNA chain.
    • Zidovudine is another example – deoxythymidine analog. Hepatic glucuronidation. Renally excreted.
      • The first antiretroviral agent.
      • Reduces disease progression and prolongs survival. Reduces vertical transmission.
  • Non nucleoside reverse transcriptase inhibitors
    • Bind directly to HIV1 reverse transcriptase to inhibit it.
    • Resistance develops quickly in monotherapy.
    • Delavirdine etc
  • Protease inhibitor
    • Resulting in immature, noninfectious viral particles
    • Darunavir etc.
  • Entry inhibitor
    • Intefere with virus binding and entering cell via gp120
    • Enfurvitide, maraviroc
  • Integrase inhibitor
    • Inhibits transfer of the reverse transcribed HIV DNA into chromosomes of host cells.
    • Eg Raltegravir
  • M2 proton pump inhibitor and inhibition of uncoating of viral RNA
    • Amantadine- increase dopaminergic function, SE -acute psychosis



Disinfection vs. sterilisation (MCQ).

  • Disinfection means killing microbes but does not mean all microbes
  • Sterilisation is a process of killing all life forms present on a surface – done with heat, chemicals, irradiation, high pressure, filtration or a combination of the above



  • Gentamycin
  • Ciprofloxicin
  • Metronidazole
  • Isoniazid
  • Tell me about anti-TB therapy


  • Rifampacin
    • Inhibits bacterial DNA dependent RNA polymerase
  • Tell me about the treatment of Malaria
    • Plasmopodium falciparum
      • Doxycycline(or clindamycin) + quinine
    • Plasma podium vivax / ovale
      • Hydroxychloroquine  + primaquine
    • P Malariae
      • Cholorquine
  • Tell me about the principles of HIV treatment